Outdoor signs started out as static signs. The accuracy of these signs was checked before the sign was mounted. However, some industries and government entities found it desirable to have signs that could be easily changed. For instance, retail gasoline stores generally display the price they are charging for various grades of gasoline. One solution is a sign that has manually placed characters that fit is certain slots on the sign. These signs are verified by the person placing the characters, however it is common for the characters to be blown off or fall down and the sign be incorrect. A more advanced sign is a variable message sign that has lights that may be controlled to make a display. These signs are used by retail outlets, banks, highway departments, sporting arenas and others. These signs are much more convenient to use. However, when the lights are not working it is possible for the sign to be illegible or even incorrect. This can led to irate customers or in the case of highway signs misdirected drivers.
Thus there exists a need for a feedback circuit for display signs that allows the user to remotely monitor the legibility of variable message signs.